NN 2015 12 th INTERNATIONAL CONFERENCE ON NUCLEUS-NUCLEUS COLLISSIONS June 21-26, 2015, Catania, Italy Isospin influence on the decay modes of systems produced in the 78,86 Kr + 40,48 Ca reactions at 10AMeV Brunilde Gnoffo for NEWCHIM-ISODEC Collaboration Istituto Nazionale di Fisica Nucleare - Sezione di Catania
Outline - The Physics Case - The Experimental Method - Experimental Results IMF behavior Global features - Conclusions and Outlook
Physics case Heavy-ion induced reactions with stable and radioactive beams are ideal to explore the response of nuclei under different stress conditions Energy domain E < 15 MeV/A is dominated by fusion processes in competition with binary reactions Both these processes are influenced by many parameters : - nuclear structure and N/Z of the system - angular momentum, dynamical effect -> quasi-fission Decay modes populate the whole mass/charge domain from evaporated light particles up to the symmetric fission fragments, with the IMF in between the decay mechanism are influenced by different parameters : E*, J, N/Z, nuclear structure
Experimental method ISODEC CHIMERA@LNS E = 10 AMeV 78 Kr + 40 Ca -> 118 Ba and 86 Kr + 48 Ca -> 134 Ba Formation of two composite systems that are different for 16 neutrons 118 Ba 134 Ba E*(MeV) 215 270 V B (MeV) 90 87 (N/Z) tot 1.11 1.39 -> possibility to explore the dependence of the formation and decay mechanisms of the composite system on the isospin (N/Z) S. Pirrone et al., EPJ 17 (2011) 16010; G. Politi et al., EPJ 21 (2012) 02003; S. Pirrone et al., AIP Conf. Proc. 1524 (2013) 7; G. Politi et al., JPS Conf. Proc. to be published 2015; S. Pirrone et al., Journal of Physics: Conference Series 515 (2014) 012018; ISODEC Experiment complements the experiment E457S (GANIL) -> study of the reactions 78,82 Kr + 40 Ca at 5.5 AMeV with the INDRA device same neutron-poor system -> influence of the energy of the entrance channel G. Ademard et al., PRC 83 (2011) 054619 4
Experimental method CHIMERA device at INFN-LNS in Catania ITALY 4π device 1192 Telescopes Si (300μm) - CsI(Tl) Forward part 1 <θ<30 688 modules 9 Rings 100cm<d<350 cm Backward part 30 <θ<176 504 modules Sphere R=40 cm A. Pagano et al., NPA681 (2001) 331 Precise measurement of E, TOF, Velocity, θ, φ Different identification methods: PSD Si, E-ToF, DE/E, PSD CsI 5
Experimental method CHIMERA device at INFN-LNS in Catania ITALY 4π device 1192 Telescopes Si (300μm) - CsI(Tl) Forward part 1 <θ<30 688 modules 9 Rings 100cm<d<350 cm Backward part 30 <θ<176 504 modules Sphere R=40 cm G. Politi et al., IEEE NSS Conference Record (2005) N28-5 Precise measurement of E, TOF, Velocity, θ, φ Different identification methods: PSD Si, E-ToF, DE/E, PSD CsI 6
Experimental results IMF behavior Different isotopic composition and relative richness of the Carbon for the two systems E. De Filippo, A. Pagano, EPJA681 (2014) 32 7
n-rich n-poor Experimental results IMF behavior Mass distributions of different Z for the n-poor system 78 Kr + 40 Ca and for the n-rich system 86 Kr + 48 Ca at θ lab = 21 Li Be B A=6 A=7 A=10 A=7 A=9 A=11 A=7 A=9 A=11 A=6 A=10 8
Experimental results IMF behavior Charge Yields for IMF of the reactions 78,86 Kr + 40,48 Ca in the range Lab = 10-16 The IMF yields exhibits an odd-even staggering, that is more pronounced for the n-poor system In agreement with: I. Lombardo et al., PRC 84 (2011) 024613 G. Casini et al., PRC 86 (2012) 011602 9
Yield (a.u.) Yield (a.u.) Experimental results IMF behavior Preliminary comparison with DiNuclear System (DNS) code S.A. Kalandarov et al., PRC 82 (2010) 044603 charge Z charge Z Simulation performed for the TOTAL cross section and normalized at Z=5 DNS seems to reproduce slightly better the n-poor system
Experimental results IMF behavior Preliminary comparison with Gemini ++ code Simulation performed for the TOTAL cross section and normalized at Z=14 Gemini++ seems to reproduce slightly better the n-poor system
Experimental results IMF behavior Average velocity for Z= 3-17 in the center of mass frame for different Z and at different θ lab Velocity seems to be independent of the emission angle for all the fragments -> high degree of relaxation of kinetic energy Signature of a binary process dominated by the Coulomb interaction between the considered fragment and its complementary partner 12
Experimental results IMF behavior Experimental average values Viola values Average values of the experimental velocity ( from Q lab =10.75⁰ to Q lab =15.25⁰) in the center of mass frame compared to the values obtained with the systematic of Viola, with the correction for the asymmetric fission D.J. Hinde, NPA472 (1987) 318 13
dσ/dω(a.u.) dσ/dω(a.u.) Experimental results FF behavior Angular distributions in the center of mass frame for fission fragments n-poor Z=31-32 Z=18 Z=29-30 Z=15 Z=12 Z=27-28 1/sinθ fit -> high degree of relaxation Production via a long lived system Similar results for the n-rich system 14
dσ/dω(a.u.) Experimental results ER behavior Angular distributions in the laboratory frame for groups of Z (from Z=41-42 up to Z=45-46) n-poor Z=45-46 Z=43-44 Z=41-42 These angular distributions are very strongly forward peaked as it is expected for the evaporation residues. 15
Vel (cm/ns) Experimental results ER behavior Extracted centroids V ER for the evaporation residues vs laboratory angle compared to V CN *cos θ lab Z=41-42 Z=43-44 Z=45-46 θ lab ⁰
Experimental results Global features M tot P tot plot for complete events selection: Multiplicity 2 0.8 M CN M tot 1.1 M CN 0.6 p tot /p beam 1 M tot 78 Kr + 40 Ca P tot /P beam 17
Experimental results Global features Plot mass-vparallel of the reaction products with complete events selection -> important information on the competition between the reaction mechanism ->very preliminary analysis seems to show that there is a higher ER/FF ratio for n-poor system compared to the n-rich one ER FF-QF ER FF-QF V CN V CN vp vp 18
Experimental results Global features ISODEC experiment E457S experiment 78 Kr + 40 Ca FF 10 AMeV FF QF 5,5 AMeV M 2 QF ER 78 Kr + 40 Ca ER M 1 Preliminary comparison with the INDRA results of the reaction 78 Kr + 40 Ca at 5.5 AMeV G. Ademard et al., PRC 83 (2011) 054619
Experimental results Global features 78 Kr + 40 Ca 5.5 AMeV G. Ademard et al., PRC 83 (2011) 054619 78 Kr + 40 Ca 10 AMeV Present work Very Preliminary comparison with the production cross section of the IMF in the reaction 78 Kr + 40 Ca at two different energies
Conclusions The results of the analysis of the reactions 78,86 Kr + 40,48 Ca at 10 AMeV are presented: The kinematical characteristics and the angular distributions of the fragments detected seem to indicate for both reactions a high degree of relaxation of the composed system The IMF cross section is more flat for the neutron poor system at the higher energy The results put in evidence the influence of the neutron enrichment of the entrance channel on: - Different isotopic composition and relative richness of the reaction products for the two systems. - Odd - even effect, Staggering, in the IMF charge distributions -> stronger for the n-poor system. - Sizeable differences for the different reaction channels: FF, QF and ER -> there is a higher ER/FF ratio for n-poor system compared to the n- rich one 21
Outlook Data analysis are in progress : Cross sections calculations for different mechanisms to confirm this first qualitative observation Study of the Coincidence between LCP-FF, LCP-ER,LCP-IMF More precise comparisons with theoretical predictions to provide indications on the isospin influence on the reaction mechanism and fragments production
Outlook For a comparison with the results obtained with the stable beams, a LOI was presented at the Second SPES International Workshop at INFN-LNL in May 2014 by using radioactive beams for studying the reactions: 92 Kr + 40,48 Ca 10 AMev 132,140 Ba* E* ~ 320 MeV These reactions lead to the formation of CN with N/Z =1.5 greater then the ratio obtained with stable beams. -> study of the evolution, with isospin asymmetry, of the reaction dynamics and competition between different decay modes -> interplay between nuclear structure and reaction mechanism in the emission process
EXOCHIM ISODEC collaboration B.Gnoffo 1, S.Pirrone 1, G.Politi 1,2, M.LaCommara 3,4, J.P.Wieleczko 5, E.DeFilippo 1, P.Russotto 2,6, M.Trimarchi 7,8, M.Vigilante 3,4, G.Ademard 5, F.Amorini 6, L.Auditore 7,8, C.Beck 9, I.Berceanu 10, E.Bonnet 5, B.Borderie 11, G.Cardella 1, A.Chbihi 5, M.Colonna 6, A.D Onofrio 4,12, J.D.Frankland 5, E.Geraci 2,1, E.Henry 13, E.LaGuidara 1,14, G.Lanzalone 15,6, P.Lautesse 16, D.Lebhertz 5, N.LeNeindre 17, I.Lombardo 4, D.Loria 7,8, K.Mazurek 5, S.Norella 7,8, A.Pagano 1, E.V.Pagano 2,6, M.Papa 1, E.Piasecki 18, F.Porto 2,6, L.Quattrocchi 7,8, M.Quinlann 13, F.Rizzo 2,6, E.Rosato 3,4, W.U.Schroeder 13, G.Spadaccini 3,4, A.Trifirò 7,8, J.Toke 13, G.Verde 1 1) INFN - Catania, Italy 2) Dipartimento di Fisica e Astronomia, Università di Catania, Italy 3) Dipartimento di Scienze Fisiche, Università Federico II Napoli, Italy 4) INFN - Napoli, Italy 5) GANIL - Caen, France 6) INFN LNS - Catania, Italy 7) Dipartimento di Fisica, Università di Messina, Italy 8) INFN Gruppo Collegato di Messina, Italy 9) IN2P3 - IPHC Strasbourg, France 10) IPNE, Bucharest, Romania 11) IN2P3 - IPN Orsay, France 12) Dipartimento di Scienze Ambientali - Seconda Università di Napoli, Caserta, Italy 13) University of Rochester, USA 14) Centro Siciliano Fisica Nucleare e Struttura della Materia, Catania, Italy 15) Università Kore, Enna, Italy 16) IN2P3 - IPN Lyon, France 17) IN2P3 - LPC Caen, France 18) University of Warsaw, Poland 24